May 18, 1999 - Iran says relations between Tehran and Britain have been upgraded to ambassadorial level.

Sept 24, 2001 - British Foreign Minister Jack Straw visits Iran to bolster an international “anti-terror” coalition after the September 11, 2001 attacks on the United States.

June, 2004 - Iran arrests eight British military personnel for straying into its waters from Iraq. They are freed after talks.

Oct 12, 2005 - British Prime Minister Tony Blair says there evidence that Iran or the Iran-backed Lebanese militia Hezbollah was the source of technology used in roadside bombs against British soldiers in Iraq. Iran denies involvement.

Oct 16 - Iran’s president accuses Britain of being behind twin bombings that killed six people in southwestern Iran a day earlier, a charge that Britain denies.

March 23, 2007 - Iranian forces seize eight Royal Navy sailors and seven marines, in the mouth of the Shatt al-Arab waterway that separates Iran and Iraq.

April 4 - President Mahmoud Ahmadinejad says he will free the 15 as a “gift” but scolds Britain for not being “brave enough” to admit they had made a mistake and strayed into Iranian waters. They arrive back in Britain the next day.

June 24, 2007 - Iran’s parliament speaker says the award of a British knighthood to author Salman Rushdie, was a shameless act. Iran’s Foreign Ministry summoned Britain’s ambassador to Tehran the previous week to protest against the honor.

June 18, 2009 - Britain says it has frozen Iranian assets of almost a billion pounds ($1.6 billion) under international sanctions imposed over Tehran’s disputed nuclear program.

June 19 - Britain protests to Iran over a speech by Supreme Leader Ayatollah Ali Khamenei who called Britain “the most treacherous” of Iran’s enemies. Prime Minister Gordon Brown has condemned violence and media curbs in Iran after the disputed June 12 presidential election led to days of protests.

June 23 - Britain expels two Iranian diplomats after Iran forces two British diplomats to leave.

June 28 - Authorities in Tehran detain eight local British embassy staff for involvement in post-election unrest. Britain calls the arrests “harassment and intimidation.”

July 3 - EU countries summon Iran’s ambassadors to their capitals to protest at detention of embassy staff.

July 19 - Iran releases on bail the last of Britain’s local embassy workers, chief analyst Hossein Rassam.

August 8 - Iran tries Rassam on charges of espionage, which Britain describes as an “outrage”

November 25 - Iranian naval vessels detain five Britons on a racing yacht en route from Bahrain to Dubai.